In daily life, a hinge structure is usually assembled between two objects to make a foldable object, comprises the two objects, be capable of lifting-opened and closing. An existed hinge structure usually comprises a male hinge and a female hinge. The male hinge comprises a connection portion and a shaft, and the female hinge usually comprises another connection portion and a socket portion. In general, the shaft of the male hinge is rotatably assembled into the socket portion of the female hinge, the connection portion of the male is connected to a first object, and the connection portion of the female hinge is connected to a second object. Therefore, the first object can rotate by a center of the shaft to make the first object be capable of lifting-opened from the second object, or be capable of closing to the second object, so as to form the foldable object as mentioned.
Due to that the shaft of the male hinge are worn with the socket portion of the female hinge, it is usually necessary to formed with a plurality of grooves, i.e., lubrication grooves, for receiving lubricant, so as to lubricate the shaft and the socket portion when the shaft rotatably assembles into the socket portion.
In the prior arts as mentioned, a conventional hinge structure is applied for detail description. Please refer to FIG. 1 and FIG. 2, wherein FIG. 1 illustrates an exploded view of a hinge structure in prior arts, FIG. 2 is a partial sectional view along A-A direction in FIG. 1 after the shaft portion is rotatably assembled into the socket portion. As shown in the figures, a hinge structure 100 comprises a male hinge 1 and a female hinge 2. The male hinge 1 comprises a connection portion 11 and a shaft portion 12 extended from the shaft portion 11, and the shaft portion 12 comprises a plurality of diametrical protrusions 121 and diametrical grooves 122. The diametrical grooves 122 are diametrically recessed form the diametrical protrusions 121. The female hinge 2 comprises a connection portion 21 and a socket portion 22 extended from the socket portion 21.
As shown in FIG. 2, when the shaft portion 11 of the male hinge 1 is rotatably assembled into the socket portion 22 of the female hinge 2, a plurality of ring-alike spaces are formed between the diametrical grooves 122 and the socket portion 22. Thus, it is able to fill lubricants into the ring-alike spaces to lubricate the shaft portion 12 and the socket portion 22, so as the reduce the wear between the shaft portion 12 and the socket portion 22 when the male hinge 1 rotates with respect to the female hinge 2.
People skilled in ordinary arts can realize that in the prior arts as disclosed, the diametrical grooves 122 are usually formed by cutting. Moreover, ignoring the material properties of the shaft portion 12, the socket portion 22 and the lubricants, the torque that can be provided between the male hinge 1 and the female hinge 2 is decided by two factors, wherein one factor is the fit condition between the shaft portion 12 and the socket portion 22, such as slight clearance fit, close fit, loose fit, etc., and the other factor is the contact area between the shaft portion 12 and the socket portion 22.
Going with the accumulation of the rotation times of that the male hinge 1 rotates with respect to the female hinge 2, the wear between the shaft portion 12 and the socket portion 22 is more and more serious. Therefore, neglecting the expansion and shrink effect caused by temperature variation, the outer diameter of the diametrical protrusions 121 reduces with the accumulation of the rotation times of that the male hinge 1 rotates with respect to the female hinge 2, so that the fit condition between the shaft portion 12 and the socket portion 22 is gradually trending to the loose fit; however, the contact area between the shaft portion 12 and the socket portion 22, i.e., the whole contact area between all the diametrical protrusions 121 and the socket portion 22 does not increase any.
People skilled in ordinary arts can further realize that in the prior arts as disclosed, under this background, the torque, which can be provided by the male hinge 1 and the female hinge 2 will be obviously reduced with the accumulation of the rotation times of that the male hinge 1 rotates with respect to the female hinge 2. In other words, the decay rate of the torque will be apparently increased to make the male hinge 1 and the female hinge 2 become unusable any more when the torque provided by the male hinge 1 and the female hinge 2 reduces to a specified torque value.